Without limiting the scope of the present invention, its background will be described in relation to setting packers, as an example.
In the course of preparing a subterranean well for hydrocarbon production, one or more packers are commonly installed in the well. The purpose of the packers is to support production tubing and other completion equipment and to provides a seal in the well annulus between the outside of the production tubing and the inside of the well casing to isolate fluid and pressure thereacross.
Certain production packers are set hydraulically by establishing a differential pressure across a setting piston. Typically, this is accomplished by running a tubing plug on wireline, slick line, electric line, coiled tubing or another conveyance into the production tubing to a profile location. Fluid pressure within the production tubing may then be increased, thereby creating a pressure differential between the fluid within the production tubing and the fluid in the wellbore annulus. This pressure differential actuates the setting piston to expand the seal assembly of the production packer into sealing engagement with the casing. Thereafter, the tubing plug is retrieved to the surface such that production operations may begin.
As operators increasingly pursue production in deeper water offshore wells, highly deviated wells and extended reach wells, for example, the rig time required to set the tubing plug and thereafter retrieve the tubing plug can negatively impact the economics of the project, as well as add unnecessary complications and risks. To address these issues associated with hydraulically set packers, interventionless packer setting techniques have been developed. For example, a hydrostatically actuated setting module has been incorporated into the bottom end of a packer to exert an upward setting force on the packer piston. The hydrostatic setting module may be actuated by applying pressure to the production tubing and the wellbore at the surface, with the setting force being generated by a combination of the applied surface pressure and the hydrostatic pressure associated with the fluid column in the wellbore.
In operation, once the packer is positioned at the required setting depth, surface pressure is applied to the production tubing and the wellbore annulus until a port isolation device actuates, thereby allowing wellbore fluid to enter an initiation chamber on one side of the piston while the chamber engaging the other side of the piston remains at an evacuated pressure. This creates a differential pressure across the piston that causes the piston to move, beginning the setting process. Once the setting process begins, O-rings in the initiation chamber move off seat to open a larger flow area such that fluid entering the initiation chamber continues actuating the piston to complete the setting process. Therefore, the bottom-up hydrostatic setting module provides an interventionless method for setting packers as the setting force is provided by available hydrostatic pressure and applied surface pressure without plugs or other well intervention devices.
It has been found, however, that the bottom-up hydrostatic setting module may not be ideal for applications where the wellbore annulus and production tubing cannot be pressured up simultaneously. Such applications include, for example, when a packer is used to provide liner top isolation or when a packer is landed inside an adjacent packer in a stacked packer completion. In such circumstances, if a bottom-up hydrostatic setting module is used to set a packer above another sealing device, there is only a limited annular region between the unset packer and the previously set sealing device below. Therefore, when the operator pressures up on the wellbore annulus, the hydrostatic pressure begins actuating the bottom-up hydrostatic setting module to exert an upward setting force on the piston. When the packer sealing elements start to engage the casing, however, the limited annular region between the packer and the lower sealing device becomes closed off and can no longer communicate with the upper annular area that is being pressurized from the surface. Thus, the trapped pressure in the limited annular region between the packer and the lower sealing device is soon dissipated and may not fully set the packer.
Accordingly, a need has arisen for improved packer for providing a seal between a tubular string and a wellbore surface. In addition, a need has arisen for such an improved packer that does not require a plug to be tripped into and out of the well to enable setting. Further, a need has arisen for such an improved packer that is operable to be set without the application of both tubing pressure and annulus pressure.